You are sitting there, you have a nice provolone and you want Mac n' Cheese but wait. You don't have milk. The horror!
Can you still make it taste great?
You can do it without milk. Maybe add a little bit of extra butter, and be careful how much water you add, start with less, and add more as you need. It just might not taste as creamy.
For the future, I might suggest picking up a small box of powdered milk. I very rarely keep milk in my house, but I keep a box of powdered milk in case I'm cooking something that calls for it. It virtually never goes bad, and it's really convenient to have around, sometimes.
A can of evaporated milk, unsweetened, does wonderful things in Mac n' Cheese as well as mashed potatoes and gratins. I assume the powdered milk adds the same missing flavor and thickening properties to water?
I make a Mac n' cheese recipe with no dairy. One cup of provolone, half pound of macaroni, and two tablespoons of butter.
Boil the macaroni in salted water then drain and mix in the butter and provolone back in the same pot with the drained macaroni and that's it. I really like it a lot.
For milk itself, plain Greek yogurt instead of milk works really well if you happen to have it. I like it more than milk actually.